Authors:	Masciocchi, Giovanni
Advisor:	Kläui, Mathias
Title:	Strain control of magnetization for magnetoresistive sensors
Online publication date:	8-Nov-2023
Year of first publication:	2023
Language:	english
Abstract:	This thesis focuses on the magneto-elastic interactions in thin films and their significance in technological applications with particular focus on sensors. The magnetostriction, constant which determines the strength of these interactions, plays a crucial role in various applications. For instance, strain immunity is essential for magnetic sensors to reduce strain cross-sensitivity, particularly in the case of flexible substrates. On the other hand, to sense strain mate- rials require giant strain effects. The optimization of the magnetic sensing layer, including strain anisotropy, is crucial for magnetic sensors performance, depending on their specific application requirements. The first part of this thesis discusses the characterization and the engineering of the strain-dependent material properties for the development of the free layer of magnetic sensors. The focus is on two material platforms: a Ni/Fe multilayer and Permalloy. The use of He+ ion irradiation as a post-deposition technique is explored to control magnetostriction and enhance magnetic softness. The strain dependence of anisotropy and magnetization compensation is explored in another material platform, Co/Gd synthetic ferrimagnets, that has the unique ability to switch their magnetic state using a laser pulse. In the second part of this thesis, the control of domain walls using strain is extensively studied for their applications in memory devices and magnetic sensors. Domain walls offer non-volatile positioning and energy efficiency in various applications. However, the influence of mechanical strain or stress on these sensing components has been overlooked. In our studies, we highlight the importance of considering mechanical strain in actual devices, exploring the effects of different types of strain on a sensor-type device. Uniform strain and its compensation through material preparation are discussed, along with the conceptualization and realization of a new magnetic sensor based on spatially variant strain. Furthermore, the impact of time-dependent strain on domain wall devices in the presence of surface acoustic waves is investigated. By considering these factors, a comprehensive understanding of the behavior and optimization of free layer of magnetic sensors under different strain conditions is achieved.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik MaxPlanck GraduateCenter
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-9615
URN:	urn:nbn:de:hebis:77-openscience-c0ab8101-5223-4e27-925f-7d85510130e05
Version:	Original work
Publication type:	Dissertation
License:	CC BY
Information on rights of use:	https://creativecommons.org/licenses/by/4.0/
Extent:	v, 256 Seiten ; Illustrationen, Diagramme
Appears in collections:	JGU-Publikationen